Telephone system



Aug. 25, 1931. c. E. STEVENS ET AL TELEPHONE SYSTEM 2 Sheets-Sheet 1 Filed April 24, 1950 FIG. I

LNVENTOR CHARLES STEVENS ARMAND MAMOR ATTORNEY Aug. 25, .1931.

'c. E. STEVENS ET AL 82 TELEPHONE SYSTEM Filed April 24, 1930 2 Sheets-Sheet 2 51.7. r: aim-1 315.121

INVENTOR CHARLES E. srcvsus ARMAND MAMOR BY y E ATTORNEY Patented Aug. 25; 1931 oNiTE 'sTATEs PATENT QFF CEEQ I en'ennns EDVJAB-D STEVENS AND ARMAND MAMQR, or ANTWERP, BELGIUM, essienons To INTERNATIONAL STANDARD ,ELECTRIQ CORPORATION, or NEW YORK, N. Y.

TELEPHONE SYSTEM Application filed April 24, 1930, Serial No. 446,876, and in Great Britain July 1?, H29.

This invention relates to telephone systems and more particularly to telephone systems of the kind in which connections to the subscribers lines of an automatic or E semi-automatic telephone system are es-' the establishment of a connection between the subscribers of the exchanges or between an operator and I a wanted subscriber. Hitherto it has also been usual to use different trunk lines for connections in op-.

posite directions. v According to a feature of this invention, a trunk line is provided which is adapted to two-way working. This feature'is particularly useful'in cases where the outgoing lllttfllc of an automatic exchange is too small during certain hours to justify the presence of a toll operator at this exchange, as it may be the case during night hoursand with a rural exchange. In such a case it is therefore desired to place the outgoing traflic of this exchange under the exclusive control of an operator located at the desired distant exchange during such hours.

According to a further feature ofthe in-' vention this is obtained by adapting the said trunk line for use as a dialling trunk for calls from a distant exchange to the automatic exchange and as a recording trunk for calls in the opposite direction;

trunk from the local'toll position and to prepare the connection of the local recording trunk to the outgolng trunk circuit which is completedupon the call being extended from an automatic subscriber to the said local recording trunk. Means may also be provided which, upon such a call, cause the distant toll operator.

- For this purpose a switching device or' transmission o1 an alternating current i'1'n pulse to the distant toll position toindicate therein'the presence of a-call, and further; more means may be associated with the said local recording trunk-which upon such. a connection become eifective to make the local recording trunk busy for other calls, and toput it under the exclusive control of the According to still another feature'orl? this invention means are provided at the auto-- matic exchange end of the trunk line which upon a call from the distant exchange ce: operate with the switching and controlling devices of a connecting circuit attached to the trunk line to transmit alternating cur rent impulses to thedistant exehange'iior the purpose of progress indicat on and-the supervision of the connection. The said means may comprise a group of iolaysconv trolled by the connecting circuit at the auto-- matic exchange and at the distant exchange a group of relays which are related. to one another in such a manner that different signals are given to the toll operator by sub sequent alternating current impulses ceived from the automatic exchange;

-Aceording to another feature the, relay device is provided in the said connecting circuitwhich upon apremature release of a connection takes care ofany new call inltlated by the said toll operator during the release of the connecting circuit, the

said relay device being caused-to operate upon sucha call and to lock up lIl order to restore the apparatus of the connecting circuit to normal and to start its operation for the said new call. The'said relay device" may be also arranged to take care o-ffl:'aulty calls, which for instance may be created by discharges on nelghborlng' l1nes, in which case it causes the connectingjcircuit to re store to normal.

Further features of this invention will change, a local recording trunk and alocal toll operators position; whereas Fig. 2 shows a connecting or cord circuit which is adapted for use with the said incoming trunk circuit.

Referring now to Fig. 1, A is a toll operators position located at a distant toll ex change from which a trunk line T is leading to an automatic exchange B.

At the toll exchange end of this trunk there are provided a jack LJ and a lamp CL, which serve for both outgoing and in-' coming calls. Further, an individual dialling key DK and an individual ringing key RK are associated with this trunk line. At the automatic exchange B, this trunk terminates on a toll 1st group selector TIGS (Fig. 2) and by means of a certain number of relays, a call can be originated by the toll operator: It may be seen from the drawings that the toll trunk line T is connected straight to the cord circuit CC, but it will be readily understood that it is also possible to associate the cord circuit with a line finder number of such trunk lines. A call originated by a subscriber of the automatic exchange B is extended by switching means which are not shown in the drawings to the local recording trunk LT. This local recording trunk is thereupon connected to the trunk line T and the call will be received at the distant exchange to position by means of a lamp signal. In the latter case, the trunk line is disconnected from the toll 1st group selector TIGS.

The circuit operation is as follows:

A. T OZZ to automatic exchange When the toll operator plugs into the line jack LJ (Fig. 1) relay Tr operates and on its left change-over combination it switches over the front contact of the incoming impulse repeating relay Dr to the set of relays J1, H1 and K1, the functions of which will be given later, and at the right change-over combination of T7, the circuit for relay Ar is closed. The latter relay operates slowly, having a resistance in series with its winding, and so allows Br to operate via the back contact of Ar to front of Tr, and to be saturated before its circuit at the back of AP is opened. To the front of Br, relay Er also operates, and at its front contacts a short alternating current impulseis sent out to the toll trunk line. In fact, after relay Ar has operated and the circuit for B2" is opened, the latter relay releases slowly, and in turn Er also releases. At the right inner front of Ar, the resistance in series with its winding is short circuited, and at the left outer front of the same relay, a circuit is closed for relay Cr, which remains energized during the time of the connection. At the front of G1, a circuit is prepared for Br, which circuit will be completed when Tr releases at the end of the connection.

By the alternating current impulse sent out to the toll trunk line, the alternating current impulse relay Ram in the automatic exchange operates, and to its front Rbr also operates. By the front of RM and via the back of Rite sequence switch R of the toll group selector is moved out of its normal position and runs to position 8, where the toll group selector circuit picks up a free register and then advances to the position in which it awaits the dialling.

hen relay RIM" in the incoming trunk circuit operates, relays G1 0" and BTTZ (Fig. 2) operate in parallel, to the front contact of relay R61", and by the front of BW'Z the sequence switch of the toll group selector is moved out of position 1. Relay BWZ locks until 1% via its front contact. At the lef: middle front of Brrl, ground is connected towards relay Rd, in the local recording trunk LT Fig. l) which operates and makes the latter circuit busy assuming that the night key NK is thrown. tion 1 the ground for the mentioned relay is supplied from the right outer contact of cam F. In position 2, relay GZr is still con nected towards the front of relay Rb), and G1?" will release only after the impulse is over, and at the back of G11 the sequence switch will be moved out of position 2.

Beginning from position 2, the slow releasing relay Pw" is connected via cam K to the back of RM, and from this moment on the selector is under control. of this r lay. In fact, this relay will keep energized during the train of impulses, and will release only in case a release impulse is given, which is long enough to cover the releasing time of PW. Relay PW controls, over its back contact the break down relay BWZ, which, when once operated, locks between 3/18 to cam F. The functions of this relay will be given in connection with the various cases of premature release.

In position 3, the register chooser BC which is shown at the bottom of Fig. 2 is connected via cam I to the back of G22 and it will start to hunt for free register which is not shown in the drawings. lVhen a free register is picked up relay Gt?" operates via the test brush g of the register chooser and cam T, by its high resistance winding. and as soon as it makes its front contact it introduces its secondary winding in series with S711", in parallel to its high resistance winding, making the register busy. Belay Sh? is slow acting, and is provided to prevent double connections. To the front contact of S720", relay GZr operates, and at its front contact the sequence switch moved out of position 8. Beginning in position 3, from cam F left inner, via the back contacts of BWZ and Pgr, a ground is connected to the armature of Bfr (Fig. 1) by which re- After posiback of S0 1" and via cam M, to energize reLayBfr, in the incoming trunk circuit, and by this change in the trunk circuit an impulse is. given towards the toll operator, causing the supervisory lamp CL to flash, This is an indi cation to the toll operator at the distant exchange that she may'start dialling.

The combination of relay Bf? and the slow releasing relays S0 1- and S0 1" in Fig. 1 serves to give impulses, towards the .toll operator, of the progress of the call. This is done in the following way: As soon as relay Bfr operates, it disconnects at its back contact relay S0 1", and prepares a circuit for relay S0 1". Since relay S0 1" is slow releasing, relay R01" will get a chance to operate, for a short time,via front of Sogandfront of Bfr. By. fronts of RM an impulse of alternating current is sentout to the distant toll ofiice. .To this impulse, the alternating impulse relay R7 at the toll position operates and D1- also operates in turn. It may be remarked thatthe lamp CZ associated With the line jack LJ is caused to light,v as soon as the operator inserts the plug, via

the following circuit: back of Gmback of H9" tothe right innerfront of'T'r.

Bythe impulse received, a circuit is closed at the front of Dr forrelays K1" and H1 in series. Relay K1, being a marginal relay, will not operate, but relay Hr will operate and locks via its front contact to the right inner frontof T1". At the right outer front of H?" a circuit isprepared for relay Jr, to the back contact of Dr, and as soon as the impulse is over, relayJr also operatesfand locks .to its own front contact. At the change-over combination of H1, the lamp Cl is switched over, via back of Kr, tothe flashing interruptersFLI. The lamp will start flashing, and this is an indication that a register is picked up and the toll operator may start dialling;

The operator will throw the dialling key- DK and will dial the full number wanted. When the dialling key is thrown,relay Sr, operates'in series with the dial, andwhen the dial is Wound up, relay E7" also operates to the off-normal contact of the dial. At every opening of the dial, relay S1" isreleased, and at its back contacts and ;via

. front of E7, the dialling impulses, by means of the alternating current, are sent out to the line. I

As mentioned in the foregoing the toll group selector circuit has advanced to the dialling position 4 in which the instepping circuit of the register, viabrushes a and b, is closed via back contact of Irv". and

cam P, in serieswith a resistance. At the same time, the impulse repeating relay Ir)" is connected via cam L, back of P97" towards the front of R61". The impulses sent by the toll operator are received by the alternating current relay Bar and by the impulse repeating relay Rbr, which transmits the impulses to the register.

After all digits have been sent in,.the dialling key is restored, andthe operator awaits the completion of the connection.

When the register is ready first selection relay G'Zr operates via cam E and brush cl to the register, and at the front of GZr the sequenceswitch is advanced to make the to position 6, where .relay Glr remains locked by its left hand front contact, via cam S and brush 0?, to the same circuit. In position 6, the trip spindle P of the selector is set,-via cams C' and I, to'the front of GM, in the known manner, and'after the last impulse, when theshortcircuiting contact on INT2 is opened, Glr releases, and on its back contact drives the sequence switch out of position 6. In 6%, Glr is connected via cam Dfback of BWZ to the back contact'of Gt?" and to the front of-Glr the brush ,car-

riage P will start to rotate, via cams C and I. When a free trunk has been picked up, Gtr energizes by its outer and inner windings in series, and by its front contact it introduces its secondary winding, making the trunk busy. At the back, of Gtr, the circuit for GZr isopene'd, andiat the back contact of the latter,.the sequence switch is driven out of 7, through'8 and 9 to the selection beyond'position 10 Ifthe brush carriage should not succeed in picking up a trunk in position 7 due to double-test, repeated hunting in position 8 will take place, since GZr will. again energize in the same circuit to the back of G251". If, due to a premature release, the brush carriage is started out of its normal position but does not pick up a free trunk, it will be restored in position 9 since GZ? will find 'a'circuit via cam E to the back of Gt7,"tlI1Cl will'drive the brush carriage 'home.. When reaching the home position, the contact .of' G.INT.will be closed andGtr will be caused to" energize, disconnecting Glv' and'on the back of the latter the sequence switch will be moved out of 9 In. position 10 the registers fundamental circuit is connected via brushes 0 and d and cams R and S towards the next selectors. It will be remarked that relay C81 is connected towards the register via cam O and bru'sh"e beginning from 8 10%, and thus the cord circuit is under the control of the register. When-the register has completed the selection, the ground for Csrfis removed in the register,, and this relay releases and in turn Glr operates to'thet, back of. CS7", and moves the sequence switch out of position 10 running to position 12,. which is the ringing'or busy? position. In

11 A, the ground at, cam M is opened, and

this causes the release of relay Bfr, in the trunk circuit.

It will be remembered that at this moment, relays Hr and Jr are energized, and lamp CL is flashing. At the incoming end, relay Bfr is energized, and also S0 1 is energized, via back of S0 1 and front of Bfr. When the selection is completed and the toll group selector leaves the selection beyond position, the circuit for relay Bfr is opened as already mentioned and this relay releases, and in turn So r also releases, but being slow releasing, relay Rcr will energize for a short while, via front of S0 7" and back of Bfr,

' thus sending out again a short impulse towards the distant toll ofiice. By this second impulse, received by relays Br and Dr, relay Hr will be short circuited via the right inner front of J r, and thus Hr will release, but at the same time, the marginal relay Kr will operate via the right inner front of Jr to front of Dr, and will look by its outer winding to the front of Tr. Relay Jr will keep energized by its inner winding, via its left hand front to the front of Dr, as long as the impulse lasts, but will release when the impulse is ever, since the circuit of its outer winding is opened at the front of Dr and the circuit of its inner Winding is opened at the front of Hr. Lamp CL will stop flashing and will light steadily, via back of Hr to front of Tr, as at the beginning.

If the called subscribers line has been found free, the final selector will run to the ringing position and will send out intermittent ringing in the regular way. As soon as the called subscriber answers, relays Car and (lsr operate in series, via the subscriber loop, and at the front of Car the sequence switch is moved out of position 12, running to the talking position 13 where relay Bfr is placed under the control of the automatic subscriber. In this position relay Bfr, being connected via cam M to the front of Csr, will again operate and again an impulse is sent out to the line by means of the slow releasing relays S0 1 and Sa r, which impulse again causes the energization of relay Hr and in turn also of relay Jr. \Vhen Hr'opeiates, the lamp CL extinguishes and thus shows that the called subscriber is on the telephone. Any further change by the automatic subscriber will cause a change in the relay Bfr, which in turn will always send out an impulse towards the toll oflice, and will cause a corresponding change in the state of the relays Hr and Jr. In

this way, the supervision of the automatic subscriber is obtained.

If the called subscriber was found busy, and thus the sequence switch stopped in po sition l2, relay C817 is caused to energize steadily, from the final selector, and Ber will release, which relay, as may be seen, was energized beginning from 11%, via

be intermittently sent out to the line, and

lamp CL will be caused to flash, giving an indication to the toll operator that the wanted subscriber is busy. The speed of the busy flash interrupter in the group selector is different from'that of FLI and this fact allows the toll operator to discriminate between the busy flashing and the flashing caused by the interrupter FLT.

It must be remarked that if the line was found free, the battery from the final given to Cs r is only temporary, during a passing contact, and not given long enough to cause the release of the slow releasing relay Ber. If, in the talking position, the called subscriber leaves the telephone and it is desired to re-ring him, the toll operator throws the ringing key RK, and in this way relay Er is caused to energize to a ground at the ringing key, and relay Sr energizes intermittently, via the interrupter FLT. Thus alternating current is sent out to the line intermittently and to these impulses relays Bar and Rrr operate in parallel, via cam Q, back of Pgr, to the front of Rbr. Relay Ber will keep energized during the interval of impulses, whereas Rrr will. release and thus the ringing relay Rsr will energize via back of Rrr and front of Bar, to ground on cam J. Relay Rsr, once energized will lock by its front contact to front contact of Bar, as long as the ringing impulses last. At the fronts of Rsr, steady ringing current is sent out to the subscribers line. It will be observed that during talking i. e. when 0817" is energized, relay Rrr is also energized to L cuit, since it may happen that the called subscriber may leave the telephone until the toll operator has established the connection at the other end.

If, on the other hand at the end of the conversation, the toll operator withdraws her plug before the subscriber releases, relay Tr releases, opening at its front contact the circuit for relay Ar, and closing at its back contacts circuits for relay Br and Er. Relay Ar releases slowly and will allow relay Er to come up via its front to back of Tr, and Or, being slow releasing, will allow Br to energize and be saturated to the back of Tr. The circuit for Er, after having been opened at the front of Ar, will be lZU kept closed at the front of Br,'andthus a long alternating current will be sent out to the toll line. Y With this long impulse relay Prr and to its back contact Brr operates and locks. By theright inner front contact the sequenceswitch is driven out of 13, through to position 17, where the brush'carriage is restored. The sequence switch then advances to position 18, where Glr checks, via cam K, to the back of Rbr, whether the impulse is already over, and if so, Glr

- operates and at its front contact drives the sequence switch to its normal position. The trip spindle P restores in position 13 /151/ and TWA/5 to its off home contact, inthe usual way.

At the toll exchange the locking circuit for relays J r, Hr, and Kr also being opened at the front of Tr, all these relays will release. v

Release from busy position 12 If the toll operator releases due to the as fact that the called subscriber has been found busy, relay Glr operates via cam D, back of Pgr to the front of Rbr, and immediately opens the ground for the armature of Bfr, which was supplied via the back contact of Glrfrom cam Gr. Awhile later, when. Prr releases, Brrl also operates and locks and drives the sequence switch through positions 12/15. At the left hand back contact of Brrl, the ground forthe armature of 'Bfr is definitely opened, to preventa falseimpulse. from being sent out to the line. the other hand relays Ber andRrr, which are energized .in position .11 A/12 to ground on cainQ, will keep energized, beginning in 12%/13 via cam'Lgto, the left middle front of Brrv; this in order to prevent Rsr from operating and sending out ringing current. 1 I

Premature release Any. kind of premature release is char,- acterized by the release of Prr and by the operation of Brrl in the regular way, In all cases, by the right-7 inner front of Brrl, the sequence switch is advanced, or in positions 7 /9 the sequence switch is advanced at the back of Glr, on account of the aircuit for the latter relay being opened rat the back of Brrl. To the left inner, front of Brr, between positions 4/10 relay Irr operates and at its back contact :the loop towards the instepping'circuitof the register is opened, andthus the registerwill be caused to release. This is necessary on account of the fact that from the selection beyond position the cord may release only from the register. lVhenever Brrl is energized, at its right outer front contact bat-' tery is connected to the inner winding of Pgr, and as soonas the releasing impulse releases is over, Pgr will also energize to the back of Rbr, and it also locks to cam F. At the right change-over combination of Pgr, Irr is disconnected from the front of'Rbr and Nor is connected to this front instead. The function of relay Nor is to register a new call, if such is originated during. the release. In fact, incase of a new call, relay Nor will energize via front of Pgr to front of Rbr, and will lock untiliposition 1. At the front of Nor, the sequence switch is moved through position 1 to '2, and the call then progresses in the regular wa .If a" premature release occurs uring the hunting for a register, test potential is placedfrom the right outer contact of Brrl,

If, due to discharges on neighbouring lines, relay Bar and Rbr inthe trunk circuit operate, and thus a call is originated, when the cord circuit becomes 7 connected to the register and no dialling follows, relay Pgr will operate from the register and lock. The sequence switch will then be driven out by the left front contact of Pgr, through all positions except the return on premature release" position, and relay Nor is again connected towards the front of Rbr, via the front of Pgr. Thus, also if a call is originated in such a case, it will be taken by relay New", and the sequence switch will be driven-beyond position 1. 7

It will be remarked that in any case, when Brrl or Pgr operates, the ground from the armature of Bfr being removed, no impulse will be sent. out to the toll operator, and

thus no false signal will be given.

A Back release If back release is wanted, connections called for under note l are to be provided, and in such a case, when the called subscriber releases, the selector may move out of posi- .tion 13 by the front of Glr, which is energized to the back of Gsr. An impulse will be given towards the toll operator in the regular way, due to the opening of the front of Csr. In this case, the sequence switch will stop in position 15, awaiting the release'from the toll operator, which feature is necessary in order not to create a new call by the release impulse. Due to the energization of Glr in '13, to the back of Csr, it will lock by its left hand front contactto cam G, and in this way lamp .GSL willlight inv position 15.

B. Automatic toll recording The local recording trunk circuit is, during the day,.connected to the local toll ofiice,

and if, during the night, it is required to transfer the calls to the distant toll exchange, the night key NK must be thrown. By the top change-over contacts of the night key, relay R724 is connected towards the front of Tm" and Tgr, and the busy lamp is disconnected therefrom. At the bottom change-over spring combination of the night key, the ordinary ringing relay Sr? is disconnected and the 50 cycle relay R09 is connected towards the front of Tar. Furthermore, at the bottom make contact of NK, relay Rrh' is connected to the group selector; this in order to make the trunk busy for outgoing calls (automatic to toll). in case the toll operator has originated a call towards the automatic exchange.

When the trunk circuit is picked up by a 2nd group selector, relay Tar operates and to its right from contact the switching relay R/m' also operates; this in order to transfer the front of Rb?" towards the relay combination Rg-r, Rf r and To the left front of Tm, relay Rcr operates and sends out a short alternating current impulse towards the distant toll ofiice. Relays R2 and Dr operate, and relay Fr operates in turn to the front of Dr and locks to the back of Gr; Lamp GL will light to the front of F1- and an operator will answer the call by plugging into the jack LJ. Relay Tr will operate, and to its front, via front of F1, relay Gr operates, disconnecting the lamp and opening the locking circuit for F1", which releases: Relay G? will lock via its front contact to the front of T7", and will remain energized during the whole connection.

lVhen the plug is inserted, relay Er is caused to operate for a short time, in just the same way as on an outgoing call, and thus a short alternating current impulse is given to the line. By this impulse, from the front of Rbogvia front of Phi, relay Rlr is caused to energize and will lock via its make before break combination and back of R99" to the front of Tgr. At the right front contact of R11, a circuit is prepared for Rfr,

and when the impulse is over, the latter re lay will also operate to the back of Rb? and lock to its own front contact. At the change-over contacts of Rf)", the local reeording'trunk is switched over to the toll line, and the bridge relay B m will operate via the repeating coil. At the left outer front contact of RfT, a circuit is prepared for relay P91 towards the front of Rbr.

Due to the operation of BW, the local recording trunk is kept. busy until the toll opof Ty). At theright change-over combine tion of R97, the circuit of R19" is opened, which relay releases and in turn Rfr will also release. Thus the toll line will be disconnected from the local recording trunk. Relay Rim" will remain energized via the front of Rgr t0 the front of Row, as long as the impulse lasts. VJ hen the impulse is over, relay Rim" will also release. lVhen Rf? releases, relay Br?" also releases and tune the local recording trunk is under the control of the automatic subscriber only. lVhcn the automatic subscriber releases, relay Ty?" will release and Rgr also releases in turn, and everything will be in the normal condition.

7 If the automatic subscriber releases first, relay R91" will keep energized only as long as the releasing impulse lasts, since, after the release of Rfr and Br)", relay T97 will. also release. It can be seen from the above that the local recording trunk is kept busy until the toll operator releases, even if the automatic subscriber should release first.

It may be seen that when the night key NK is not thrown, the two circuits, i. e., the long distance dialling toll trunk and the local recording trunk, are independent of one another, and either of them can be used Without interfering with the other.

Although this invention has been shown and described as applied to a particular system, namely a machine driven telephone system it is not limited but only in accordance with scope of the invention as defined by the appended claims.

What is claimed is:

1. A telephone system comprising a toll exchange, an automatic exchange, a two wire trunk extending between said exchanges, means at said toll exchange for transmitting alternating current impulses over said trunk to said automatic exchange to position automatic switches therein and means whereby said trunk is adapted to be employed as a recording trunk for calls from said automatic exchange to said toll exchange.

2. A telephone system in accordance with claim 1 wherein a relay device is located in said automatic exchange and wherein upon the extension of a call originating in the automatic exchange to a local recording trunk, said relay device is adapted to be 0perated to effect the connection of the local recording trunk to said two-wire trunk and the transmission of an alternating current impulse to said toll exchange to indicate the presence of the call.

3. A system in accordance with claim 2 having a second relay device associated with said local recording trunk and wherein said second relay device is adapted to be operated upon the connection of the local recording trunk to the two-wire trunk to busy the ISO two-wire trunk and to place the local recording trunk under the control of the toll exchange independently of the calling subscribers line. r

4. A system in accordance with claim 2 having a switching device associated with the local recording trunk and wherein said switching device. is adapted to disconnect the normal connection of said local recording trunk and connect the latter to alternating current receiving and transmitting means.

5. A telephone system comprising an automatic exchange, a distant exchange,a trunk ine extending between said exchanges, means adapted to transmit alternating current impulses from said distant exchange to said automatic exchange over said trunk, and means located at said automatic exchange adapted to transmit to said distant exchange over the said trunk alternating current impulses to give a progress indication and supervision of the connection.

6. A system in accordance with claim 5 wherein said means located at the automatic exchange comprises a group of relays adapted to be controlled to effect the transmission of said alternating current impulses. v

7. A system in accordance with claim 1 wherein a group of relays is provided 'at the toll exchange and is associated'thereat with said two-wire trunk, and wherein the relays of the group are so related to one another that different signals are adapted to be given by subsequent alternating current impulses received from the automatic exchange; 7

'8. A telephone system comprising a first exchange having a toll position a second exchange having automatic switches, a trunk extending between said exchanges, means for transmitting alternating current im-.

pulse over said trunk, a relay device at said second exchange adapted to enable the handling of a new call while the normal circuits are being restored as a result of a premature release of a previous call.

9. A system in accordance with claim 8 having an alternating current impulse receiving relay at said second exchange wherein said relay device, at the second exchange, upon a premature release is adapted to be placed under the control of said impulse receiving relay and to be "operated upon the initiation of said new call and to lock up to restore the circuits and then effect their re-operation for said new call.

10. A system in accordance with claim 8 wherein said relay device, is adapted to re store the circuits to normal in the event of a faulty call (i. e.. calls due to changes on neighboring lines).-

11. A telephone system comprising a toll exchange, an automatic exchange, a two- .mitting alternating current impulses over said trunk in the event such subscriber should leave his telephone when the connecting circuit is in the talking position.

12. A system in accordance with claim 11 wherein a ringing relay is provided in the connecting circuit and the said means in the connecting circuit comprises two relay devices adapted to be placed under the control of the alternating current impulse receiving relay at the incoming end of the trunk line when said connecting circuit is in the talking position whereb said ringing relay'is adapted to be contro led by the alternating current impulses transmitted from said toll exchange. I

In witness whereof, we hereunto subscribe our names this 5th day of A ril, 1930.

CHARLES EDWARD TEVENS. ARMAND MAMOR. 7 

